1. Field of the Invention
The invention relates to a method for producing an insert-molded article and a mold assembly therefor.
2. Description of the Related Art
An electronic control unit has a casing made of a synthetic resin and a printed circuit board is mounted in the casing. Various electronic components and an electronic control circuit are disposed on the printed circuit board and in the casing. Japanese Unexamined Patent Publication No. 2004-40945 discloses a grounding path for such an electronic control unit.
The electronic control unit has a metal nut and a metal collar that are held in contact with an intermediate busbar. The casing is formed by insert molding using the metal nut and the metal collar as inserts. Thus, the metal nut, the intermediate busbar and the metal collar are embedded and are connected successively. The casing can be fixed to a body while a grounding wire from the electronic control circuit is connected with the metal nut. Thus, the grounding wire, the metal nut, the intermediate busbar and the metal collar are connected electrically with the body and are grounded.
The metal nut is set in the mold by supporting a bottom part of the metal nut on a resting pin that projects from the mold. However, a pin withdrawal hole is left below the bottom part of the nut when the pressing pin is withdrawn. Thus, a potting material is used to close the pin withdrawal hole and to provide airtightness after insert molding. The potting material adds to the cost for raw material and an additional operation load is required for potting.
The present invention is developed in view of the above problem, and an object thereof is to improve operability.